AN EFFICIENT SYMPLECTIC INTEGRATION ALGORITHM FOR MOLECULAR-DYNAMICS SIMULATIONS

A new explicit symplectic integration algorithm for molecular dynamics (MD) Simulations is described. The method involves splitting of the t otal Hamiltonian of the system into the harmonic part and the remainin g part in such a way that both parts can be efficiently computed. The Hamilton equations of motion are then solved using the second order ge neralized leap-frog integration scheme in which the high-frequency mot ions are treated analytically by the normal mode analysis which is car ried out only once, at the beginning of the calculation. The proposed algorithm requires only one force evaluation per integration step, the computation cost per integration step is approximately the same as th at of the standard leap-frog-Verlet method, and it allows an integrati on time step ten times larger than can be used by other methods of the same order. It was applied to MD simulations of the linear molecule o f the form H-(C=C)(n)-H and was by an order of magnitude faster than t he standard leap-frog-Verlet method. The approach for MD simulations d escribed here is general and applicable to any molecular system.